Also, if the mission itself already has its own thread, post about it there: MSL (Curiosity), Gaia

To kick off the thread, NASA has announced that Voyager 1 has FINALLY left the Heliosphere and entered interstellar space. What's more, it did so over a year ago - on 25 August 2012 - but they weren't sure until they had analyzed the data.

NASA's press release on the subject can be found here, and a couple of videos related to it are embedded below.

They also captured a cool picture of Voyager 1's radio emissions, a sort of reversed Pale Blue dot image Our first extrasolar emissary has finally begun probing the stars

From a physical standpoint the region of space where the gravitational effect of the sun is cancelled out by that of nearby stars (i.e. lagrance point) should be the border of the solar system (and of any star system in that respect). And that is many, many orders of magnitude larger than Voyager's current position: http://voyager.jpl.nasa.gov/faq.html (scroll down to 55-60% of the document)

From a physical standpoint the region of space where the gravitational effect of the sun is cancelled out by that of nearby stars (i.e. lagrance point) should be the border of the solar system (and of any star system in that respect).

Why? There are other ways of defining the boundary of a solar system which are based just as heavily on physics. What determines which one is the 'right' one?

From a perspective of magnetic and particle dynamics, Voyager has passed beyond the influence of the Sun and is now exposed to the interstellar environment. Personally, I find this to be more physically meaningful than the point of equal gravitation which would very likely be passed without any significant environmental changes.

From a physical standpoint the region of space where the gravitational effect of the sun is cancelled out by that of nearby stars (i.e. lagrance point) should be the border of the solar system

But this border is only useful in some cases. In other cases (such as that of the Voyager science team) the astrophysical definition is more useful. I don't see what the problem is with there being multiple definitions.

Why? There are other ways of defining the boundary of a solar system which are based just as heavily on physics. What determines which one is the 'right' one?

From a perspective of magnetic and particle dynamics, Voyager has passed beyond the influence of the Sun and is now exposed to the interstellar environment. Personally, I find this to be more physically meaningful than the point of equal gravitation which would very likely be passed without any significant environmental changes.

Quote (HarbingerDawn)

But this border is only useful in some cases. In other cases (such as that of the Voyager science team) the astrophysical definition is more useful. I don't see what the problem is with there being multiple definitions.

The 1st trhee are in the quantum/nano/pico/fempto level and are stronger than the 4th at this level but the 4th, gravity, is stronger in the cosmic astronomical scale. Therefore gravity is distinguished as a type from the rest three. I find it more logical then for gravity to define the physical border of a star system. But I am probably the only one in the universe again who thinks this way

But I am probably the only one in the universe again who thinks this way

No, I usually define that as the boundary too, but you have to understand that there doesn't need to be one universal definition that everyone uses for every purpose. That'd be silly and stupid. From a space weather/particle environment standpoint, Voyager has left the Sun's influence and is in the environment that stretches between the stars. That is a clear physical boundary in space. Why is it so wrong to use it as just ONE DEFINITION FOR ONE PURPOSE?

Yes, "Voyager has left the solar system" seems to be almost a yearly journalistic headline since it passed beyond Pluto's orbit and we may see it again until Voyager leaves the Oort cloud behind. Since the boundaries of the solar system aren't precisely defined, such headlines are pointless.

I find it troubling that you are unable to distinguish hyperbolic journalistic headlines from an actual scientific announcement.

Was what I wrote that unclear? I referred to journalistic headlines precisely to distinguish that from scientific announcements. The point is that newspaper articles usually lack a definition of the extent of the solar system, which really is required since there is no universal unambiguous definition.

that there doesn't need to be one universal definition that everyone uses for every purpose

OK, but there has to be some sort of clarification (at least) so that people with lower scientific background (e.g. media, journalists) understand the context in which the above statement refers to.

Quote (HarbingerDawn)

That is a clear physical boundary in space. Why is it so wrong to use it as just ONE DEFINITION FOR ONE PURPOSE?

Because they used that one definition to suggest that Voyager 1 has left the Solar System. They should have said something like that it has crossed that particular boundary but there is still a long way to completely be regarded as flying in interstellar space.

Was what I wrote that unclear? I referred to journalistic headlines precisely to distinguish that from scientific announcements.

You're seemingly referring to this as if it were the former, when in fact it is the latter. If that's not what you meant to do, then yes it was that unclear.

Quote (midtskogen)

The point is that newspaper articles usually lack a definition of the extent of the solar system, which really is required since there is no universal unambiguous definition.

Every time a "Voyager has left the Solar system(?)" article has come up that I recall, a definition has been provided or implied.

Quote (neutronium76)

but there is still a long way to completely be regarded as flying in interstellar space.

But it is in interstellar space! The space that it is in has the same properties as the space that it will be in 2 light years from now! In what way does that not make it in interstellar space!?

neutronium76, you STILL don't seem to be accepting that there can be more than one definition for the boundary of the Solar system. There's an astrophysical definition (the one being used here, also the only one with a clear physical boundary), and then there's the more conventional and somewhat arbitrary gravitational influence definition (which, if we use your version of that definition, means that there would be no such thing as interstellar space, as you would always be within a star system).

Before writing anything else, can you please clearly answer this one question: is it not acceptable for multiple valid definitions to exist for the boundary of a star system?